Sian Lawson, senior lecturer in sports coaching at Northumbria University, suggested that segregated PE lessons were an “historic hangover from Victorian values” that see boys and girls as having different needs.

She insisted there was no physical reason to view “female bones as more breakable or girls more fragile when given the same level of exercise”.

Many teachers justify pushing girls into netball and boys towards football to avoid sexual harassment or discrimination.

But Dr Lawson said the “controlled environment” of the school playing field was the “best opportunity these potential adults have to learn to respect each other”.

The comments come amid a continuing debate over standards of childhood exercise and physical activity, particularly among girls.

Research published earlier this month by the University of Pennsylvania found that the brains of men and women were wired up differently which could explain some stereotypical male and female behaviour.

But Dr Lawson said many differences were down to cultural reasons, with school sport acting as one of the key barriers to equality.

“If everyone trains and competes on equal terms, the biologically slower can up their game, and if the fast naturally rise to the top no one should object,” she said. “If we aspire to believe in individual variation over stereotyping, and equality of opportunity, then why not let our children start with that?”

Research from the Department for Culture, Media and Sport in the summer found a quarter of girls aged five to 10 had not taken part in any sport over in the previous month – a rise of almost 50 per cent in five years.

Separate research by the Women's Sport and Fitness Foundation revealed that just over half of girls – 51 per cent – are put off physical activity by their experiences of school sport and PE lessons.

But Dr Lawson insisted that the subject could be used to actually break down barriers between the sexes.

Writing for Telegraph.co.uk, Dr Lawson quoted a Northumbria University study that found no physical distinction in the coaching required for elite male and female athletes.

She said: “There’s no physiological reason why boys should play football and girls rounders, indeed in the USA soccer is a ‘girls sport’ and baseball is ‘for boys’.

“Even within the traditionally male sports women are now showing that they can compete on equal terms, despite typically receiving less training.”

Dr Lawson added: “As an anatomist I haven't yet found a reason to see young female bones as more breakable or girls more fragile when given the same level of exercise.

“In schools we’ve already created a fairly even group by dividing children into age-based classes. More to the point we don’t segregate the class on the basis of height or strength, we segregate for gender.

“The idea of women as unambiguously weaker is so deeply ingrained that sometimes we don’t notice that we’ve made that assumption. Here we are teaching that idea to children, without questioning it ourselves.”

But the comments were branded “absurd” by traditionalists who insisted parents would be “horrified” by the idea of joint lessons.

Chris McGovern, a former independent school headmaster and chairman of the Campaign for Real Education, said: “It’s just political correctness. There are clear physiological differences between boys and girls.

“It’s possible to mix them in the early primary years but it’s just commonsense to split them when they get older and you’ve having full blown tackles in rugby and football because boys are stronger. It’s an absurd idea and it will horrify parents.”